The candidate is a Research Assistant Professor at the University of Florida. She has a professional degree in occupational therapy and a Ph.D. in Rehabilitation Science. Her long- term goal is to become firmly established as an independent investigator designing clinical studies that examine the relationships between activity, participation and quality of life (QoL) with pathophysiology, muscle strength and functional ability in children with chronic illnesses and disability. The candidate will primarily be mentored by Dr. Krista Vandenborne, with Dr. Barbara Curbow serving as secondary mentor. Each mentor, as well as the candidate's advisory committee, will help her transition from junior faculty member to an independent investigator through a combination of activities including: didactic coursework, mentored laboratory and internal/external training experiences, one-on-one meetings with mentors, attendance at seminars and conferences, execution of the research plan and manuscript preparation and grant writing. Four national experts were selected to serve on the mentoring advisory committee in order to provide the breadth of content expertise necessary for carrying out the career development and research plans. A very important component of the career development plan includes training at the National Institutes of Health for a three-month period in both year 1 and year 2 in the lab of Dr. Kenneth H. Fischbeck, Senior Investigator, Division of Intramural Research at NINDS, as well as the lab of Dr. Eric Hoffman, Research Center for Genetic Medicine, Children's National Medical Center (CNMC). The University of Florida has a strong commitment to rehabilitation research and is committed to supporting the candidate through the course of this mentored award. The specific aims of this research proposal are to: 1) Evaluate activity, participation, quality of life, pathophysiology, muscle strength, and functional ability in boys with Duchenne Muscular Dystrophy (DMD) compared to healthy age-matched boys; 2) Determine the relationships between activity, participation and quality of life with quantitative MR measures of muscle and disease severity (strength and functional ability) in boys with DMD compared to healthy age-matched boys; 3) Evaluate disease progression in boys with DMD using a longitudinal study design for measures of physical activity, participation, quality of life, pathophysiology, muscle strength and functional ability; and 4) Explore environmental and parental perceptions, attributes and behaviors that facilitate and/or inhibit levels of activity, participation, muscle strength, functional ability and quality of life in boys with DMD. Thirty ambulatory boys with DMD and 10 age- matched controls will be enrolled and physical activity, participation in daily life activities, quality of life, muscle pathology, strength and functional ability will be quantified and relationships determined between the variables and changes that occur over time. This study is designed to investigate the impact of muscle dysfunction and impaired functional ability on participation and quality of life in boys with DMD and to serve as a future guide for evaluating intervention effectiveness through comprehensive measurement of disease progression. Moreover, information from these studies will provide important clinical implications to target therapeutic interventions for children and families.